As a transfer method of semiconductor wafers, it is known that a plurality of wafers are transferred (carried) in a state in which the wafers are placed to be oriented horizontally (laid down), between a wafer storage unit called a Front-Opening Unified Pod (FOUP), and an angle alignment device (aligner) which performs the angle alignment of the wafers. To perform this transfer method, Patent Literature 1 discloses an exemplary device and an exemplary method which receive a plurality of wafers placed to be oriented horizontally and perform the angle alignment of these wafers.
In the substrate angle alignment device disclosed in Patent Literature 1, three support poles are provided to extend vertically upward on one turn table, and five support pins are arranged vertically and fixed to each of the support poles. This device includes three scooping poles provided independently of the turn table and the support poles. Five scooping pins are arranged vertically and fixed to each of the scooping poles. The three scooping poles synchronously move up and down while maintaining a vertical spacing between the scooping pins. In contrast, a vertical spacing between the scooping pins is set to be smaller than that between the support pins.
In the angle alignment method disclosed in Patent Literature 1, a wafer transfer/loading unit loads the five wafers onto the five support pins, respectively, and is retracted from the substrate angle alignment device. When the five wafers are carried into the substrate angle alignment device, these wafers are supported on the turn table via the support poles, respectively, in a state in which the wafers are placed to be oriented horizontally. Then, the turn table is driven to rotate the five wafers together, and the rotational positions of the wafers are stored. Then, the turn table is driven based on the stored rotational position, and the angle alignment of the wafer at a lowermost stage is performed. Then, the scooping poles are moved up to scoop up the wafer at the lowermost stage with the scooping pins at the lowermost stage to lift up the wafer away from the support pins at the lowermost stage. As described above, the vertical spacing between the scooping pins is set to be smaller than that between the support pins. Therefore, after the scooping poles are moved up, only the wafer at the lowermost stage can be scooped up by the scooping pins, and the remaining four wafers can continue to be placed on the support pins. Then, the turn table is driven based on the stored rotational position, the angle alignment of the wafer at a second lowermost stage is performed, the scooping poles are moved up to scoop up only the wafer at the second lowermost stage with the corresponding scooping pins to lift up the wafer away from the corresponding support pins, for the above-described reason. The above-described operations are repeated in succession, starting from the wafer at the lowermost stage, until the angle alignment of the wafer at an uppermost stage is completed. The aligned wafers (the wafers for which the angle alignment is completed) are away from the support pins, and do not rotate even when the turn table operates. In this way, the aligned states of the wafers are maintained. After the angle alignment of all of the wafers ends, the scooping poles are moved down and all of the wafers are transferred together from the scooping pins and loaded together onto the support pins.
When the above-described series of operations (carry-in operation, angle alignment operation, and transfer/loading operation) end, the wafer transfer/loading unit takes out of the angle alignment device, the five aligned wafers which are placed on the support pins and are preparing for the carry-out, and transfers the aligned wafers toward the wafer storage unit.